The Company That Employs Me has decided it needs to Change. To get the employees to understand and "internalize" the new Purpose, they're holding "Corporate Purpose, Strategy and Culture" meetings. Specifically, mandatory, 3-hour, in-person attendance meetings.

This is not a Company with a history of holding effective meetings. You could say that effective meetings are not part of the Company Culture. It seems to me, then, that a good way to start changing the Company Culture would be to start with that first meeting.